If your current LR 12.01 has the 50 community licenses in addition to the counts and protocols you had with LR V11.04, you can just prep and use those upgrade files to install a new controller with the 50 community license. If you need more than those 50, you will need to get with your account rep (HP, Orasi, etc) and order a license for the other Vuser counts and protocols.
You will Not be able to share your current pool of users with the new Load Runner (that requires Performance Center). But even with just the 50, it will let you create scenarios and do small scale tests while the other controller is busy.
Good Luck